The present invention relates to a plasma processing apparatus and, more particularly, to a plasma processing apparatus that performs plasma etching using plasma.
In a dry etching apparatus, the environment in the processing chamber changes along with the process history due to deposition of a reaction product between a wafer and etching gas on the inner wall of the processing chamber, change in temperature of parts associated with the processing chamber, consumption of the parts, and the like. Recently, as semiconductor devices are miniaturized, margins for the etching process become narrower and such a change in the environment in the processing chamber considerably affects the process results. It should be noted that this environmental change is not limited to a dry etching apparatus but is also true of other plasma processing apparatuses that perform processing using plasma.
To solve the problem described above, the process control technology, called Advanced Process Control (APC, hereinafter called an APC), has been widely applied. APC is a technology for feedback controlling or feed-forward controlling of recipes (processing conditions) of a next lot or wafer based on monitoring values during processings and/or process results to reduce process variations and to yield stable process results. In particular, the control of correcting a recipe for each wafer processing is called the Run-to-Run control or Wafer-to-Wafer control; hereinafter, these controls are also included in APC.
To implement APC, there is provided a technology described in JP-A-2011-082441. The technology described in this prior-art document is that, for a change in the process environment that cannot be acquired by monitoring process alone, certain amounts of an offset (an amount of a long-term shift and an amount of a short-term shift) are applied to each recipe to reduce a variation in the process result over time.
There is also provided a technology, described in JP-A-2011-003712, for reducing the effects of process variations to yield stable process results. This prior-art document describes a technology in which weighting coefficients as offset values used in creating the process conditions in the feed-forward control are made larger for a longer elapsed time.